1. Field of the Invention
The present invention relates to a radiator for a motorcycle for reducing noise caused by exhausted cooling air.
2. Description of Background Art
Japanese Utility Model Laid-Open Publication No. Hei 1-162033 discloses a cooling device for a radiator for a motorcycle, in which a cooling fan is positioned at an outlet for the radiator cooling air, and a cylindrical shroud surrounds an impeller for the cooling fan. The shroud has its front open end coupled to the rear periphery of the radiator, and houses a cooling fan at a rear portion. Further, an outlet of the shroud is in the shape of a bell mouth. In the present invention, the front, rear, left and right directions denote directions viewed in the plane which confronts flow of cooling air to the radiator, and an upward and downward direction denote the directions viewed from the position where the radiator is installed.
A shroud surrounding a cooling fan for a radiator is effective in reliably maintaining an amount of cooling air while a motorcycle is stationary and idling or while it is operating at low speeds. However, cooling air flowing through the shroud generates noise. Such noise can be reduced to a certain degree when the shroud uses a bell mouth structure. Since the cooling device of the motorcycle is usually exposed, it has been required to reduce the noise caused by exhausted cooling air as demand for quiet driving has been on the rise recently. Therefore, a cooling device for a radiator of a motorcycle has to not only obtain a necessary amount of cooling air but also reduce the noise resulting from exhausted cooling air.
A radiator is usually cooled by airstreams caused by a moving motorcycle. When the radiator has its rear surface covered by the shroud as in the foregoing publication, cooling air passing through the radiator cannot easily flow outwardly. Therefore, it is also required to improve cooling efficiency while the motorcycle is operating.
The presence of stays for mounting a cooling fan motor also affects such noise. A main object of the invention is to provide a cooling device for a radiator of a motorcycle that can reduce noise caused by exhausted cooling air, and a further object is to improve the cooling efficiency of the radiator while the motorcycle is operating.
In order to solve the foregoing problems, according to a first feature of the invention, a cooling device for a radiator of a motorcycle comprises a cooling fan positioned at a cooling air outlet of the radiator and a cylindrical shroud surrounding an impeller of the cooling fan. The cylindrical shroud has an inlet and an outlet which are in the shape of a bell mouth. The bell mouth shaped inlet is positioned near the rear surface of the radiator with a space maintained therebetween. Further, the space which opens around the shroud is provided between the bell mouth shaped inlet and the rear surface of the radiator.
In accordance with a second feature, a difference between a maximum diameter and a minimum diameter of the bell mouth shaped outlet of the shroud and a length of the shroud is in the ratio of 1:3 to 5.
In a third feature, a cooling device for a radiator of a motorcycle comprises a cooling fan positioned at a cooling air outlet of the radiator and a cylindrical shroud surrounding an impeller of the cooling fan. A bell mouth shaped inlet of the shroud positioned near the rear surface of the radiator with a space maintained therebetween, and the shroud is structured to rotate integrally with the impeller of the cooling fin.
In accordance with a fourth feature, the shroud has any one or both of an inlet or an outlet thereof in the shape of a bell mouth.
According a fifth feature, a difference between a maximum diameter and a minimum diameter of the ball-mouth-shaped outlet of the shroud and a length of the shroud is in the ratio of 1:3 to 5.
In a sixth feature, a cooling device for a radiator of a motorcycle comprises a cooling fan positioned at a cooling air outlet of the radiator, and a motor for driving the cooling fan and supported to the radiator using a plurality of motor mounting stays. All of the stays are inclined in the rotating direction of an impeller of the cooling fan.
According to a seventh feature, a cooling device for a radiator of a motorcycle comprises a cooling fan positioned at a cooling air outlet of the radiator, and a motor for driving the cooling fan and supported on the radiator using a plurality of motor mounting stays. All of the motor mounting stays are in the shape of a flat plate and inclined in a direction where exhausted cooling air is discharged.
According to a first feature of the invention, the shrouds has its inlet and outlet in the shape of a bell mouth. The bell mouth shaped inlet of the shroud is spaced from the rear surface of the radiator, and the open space is provided around the shroud. Therefore, it is possible to obtain a necessary amount of cooling air during the operation of the motorcycle, and to reduce the noise caused by exhausted cooling air while the motorcycle is stationary and idling, or while it is operating at low speeds, as well as obtaining a necessary amount of cooling air.
A part of exhausted cooling air that passes through the radiator of the operating motorcycle and overflows the shroud is effectively discharged outside via the open space. This promotes smooth flow of cooling air regardless of the shroud, and is effective in improving cooling efficiency and reducing noise caused by exhausted cooling air. A necessary amount of cooling air can be obtained when the motorcycle is stationary and idling, or when it is operating at low speeds. The bell mouth shaped inlet and outlet of the shroud contribute to the reduction of noise caused by exhausted cooling air.
In the second feature, the difference between a maximum diameter and a minimum diameter of the bell mouth shaped outlet of the shroud and a length of the shroud is in the ratio of 1:3 to 5. This ratio is effective in obtaining a necessary amount of cooling air and in reducing noise caused by exhausted cooling air, and can be set in a range optimum for manufacturing of the cooling device.
According to the third feature of the invention, the shroud rotates integrally with the impeller of the cooling fan, which means that there is no clearance between the shroud and the impeller. This extensively promotes the reduction of noise caused by exhausted cooling air, and accelerates exhausted cooling air. Further, since the bell mouth shaped inlet of the shroud is spaced from the rear surface of the radiator, it is possible to discharge exhausted cooling air that overflows the shroud, and to enable the shroud to rotate integrally with the impeller. Still further, the motor mounting stays can support the motor on the radiator without mounting via the shroud, which makes the mounting structure simple and light in weight.
In a fourth feature of the invention, either or both of the inlet and outlet of the shroud is in the shape of a bell mouth, which is effective in reducing noise caused by exhausted cooling air.
In the fifth feature, the difference between a maximum diameter and a minimum diameter of the bell mouth shaped outlet of the shroud and a length of the shroud is in the ratio of 1:3 to 5. This ratio is effective in obtaining a necessary amount of cooling air and in reducing noise caused by exhausted cooling air, and can be set in a range optimum for the manufacturing of the cooling device.
According to a sixth feature of the invention, all the stays are inclined in the rotating direction of the impeller, so that exhausted cooling air from the cooling fan comes into smooth contact with.the stays. This is effective in reducing noise caused by exhausted cooling air.
In a seventh feature of the invention, the stays are in the shape of a flat plate, and are inclined in the direction in which exhausted cooling air flows from the radiator. This enable cooling air to come into smooth contact with the stays, reduce noise caused by exhausted cooling air, and guide exhausted cooling air in a predetermined direction.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.